LancefieldSystem

LancefieldSystem, commonly referred to as the Lancefield grouping, is a serotyping scheme in bacteriology used to classify certain streptococcal species by the carbohydrates present in their cell wall. It was introduced by Rebecca Lancefield in the 1930s and became a foundational method for identifying clinically important streptococci. The scheme relies on precipitation reactions between group-specific polysaccharide antigens extracted from the cell wall and commercially prepared antisera. Isolates are assigned to groups, such as A, B, C, D, F, and G, by agglutination patterns or precipitation tests. The most widely recognized group is Group A Streptococcus (S. pyogenes), associated with conditions like pharyngitis, rheumatic fever, and skin infections; Group B Streptococcus (S. agalactiae) is a major cause of neonatal sepsis and meningitis.

Limitations and evolution: While historically central, the Lancefield system has limitations due to cross-reactivity and the occasional misclassification of non-groupable strains. With advances in molecular typing, including PCR-based assays and whole-genome sequencing, many laboratories supplement or replace Lancefield typing with genetic methods, although the serotyping framework remains a useful clinical shorthand and epidemiological tool. In current practice, Lancefield grouping is often used in conjunction with molecular methods and routine culture-based diagnostics; some labs still perform group-specific agglutination for rapid presumptive identification.